virtio_pci: Add support for PCIe Function Level Reset

virtio_pci: Add support for PCIe Function Level Reset

Implement support for Function Level Reset (FLR) in virtio_pci devices.
This change adds reset_prepare and reset_done callbacks, allowing
drivers to properly handle FLR operations.

Without this patch, performing and recovering from an FLR is not possible
for virtio_pci devices. This implementation ensures proper FLR handling
and recovery for both physical and virtual functions.

The device reset can be triggered in case of error or manually via
sysfs:
echo 1 > /sys/bus/pci/devices/$PCI_ADDR/reset

Signed-off-by: Israel Rukshin <israelr@nvidia.com>
Reviewed-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Message-Id: <1732690652-3065-2-git-send-email-israelr@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>